1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 
  26 /*
  27  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 /*
  32  * __rem_pio2l(x,y)
  33  *
  34  * return the remainder of x rem pi/2 in y[0]+y[1]
  35  * by calling __rem_pio2m
  36  */
  37 
  38 #include "libm.h"
  39 #include "longdouble.h"
  40 
  41 extern const int _TBL_ipio2l_inf[];
  42 static const long double two24l = 16777216.0L,
  43         pio4 = 0.7853981633974483096156608458198757210495L;
  44 
  45 int
  46 __rem_pio2l(long double x, long double *y)
  47 {
  48         long double z, w;
  49         double t[3], v[5];
  50         int e0, i, nx, n, sign;
  51 
  52         sign = signbitl(x);
  53         z = fabsl(x);
  54 
  55         if (z <= pio4) {
  56                 y[0] = x;
  57                 y[1] = 0;
  58                 return (0);
  59         }
  60 
  61         e0 = ilogbl(z) - 23;
  62         z = scalbnl(z, -e0);
  63 
  64         for (i = 0; i < 3; i++) {
  65                 t[i] = (double)((int)(z));
  66                 z = (z - (long double)t[i]) * two24l;
  67         }
  68 
  69         nx = 3;
  70 
  71         while (t[nx - 1] == 0.0)
  72                 nx--;                   /* omit trailing zeros */
  73 
  74         n = __rem_pio2m(t, v, e0, nx, 2, _TBL_ipio2l_inf);
  75         z = (long double)v[1];
  76         w = (long double)v[0];
  77         y[0] = z + w;
  78         y[1] = z - (y[0] - w);
  79 
  80         if (sign != 0) {
  81                 y[0] = -y[0];
  82                 y[1] = -y[1];
  83                 return (-n);
  84         }
  85 
  86         return (n);
  87 }